1. Field of the Invention
The present invention relates to an apparatus for controlling variable nozzles of a turbocharger, which controls the opening of a vane of each of the variable nozzles of the turbocharger mounted on an automobile through the use of an electronic control actuator.
2. Related Art
Hitherto, as an example of this kind of techniques, there has been provided a variable nozzle turbocharger control apparatus for an internal combustion engine, which is disclosed in JP-A-2001-107738. FIG. 4 shows the configuration thereof.
To give a description thereof, reference numeral 1 designates a turbocharger that has a center housing, a compressor housing, and a turbine housing.
The turbocharger 1 is provided with an air intake inlet port 1a from which air is introduced, and a compressed air supply hole 1b for supplying air, which is compressed by the turbocharger 1, to an engine 2. Also, an exhaust gas sucking port 1c to which an exhaust gas is supplied from the engine 2, and an exhaust port for exhausting the exhaust gas are provided therein. Variable nozzles (not disclosed therein) provided in the turbocharger 1 are disposed between the center housing and the turbine housing. Reference numeral 3 denotes a stepping motor. An operation piece 4 is operated by being driven by this stepping motor 3. Ring plates provided in the variable nozzles are pressed in the same direction. The size of the gap between the vanes of the mutual variable nozzles is adjusted. The flow rate of the exhaust gas blown against turbine wheels is adjusted. Reference numeral 5 designates an engine ECU (Electronic Control Unit), to which detection outputs of various kinds of sensors provided in the engine are inputted. The operation status of the engine is distinguished according to these detection outputs. Thus, the stepping motor 3 is driven and controlled. Consequently, the opening of each of the nozzle vanes of the variable nozzles is open/close-controlled. The flow rate of the exhaust gas blown against the turbine wheels is adjusted. Also, an amount of air to forcibly be fed for combustion is adjusted.
In the figure, reference numeral 6 denotes a radiator, which is connected to the engine 2. Coolant water for the engine 2 is cooled down by circulating in the radiator 6.
Then, according to this related art, the variable nozzle turbo charger control apparatus for an internal combustion engine is adapted so that upon occurrence of abnormality therein, upon cold start thereof, or upon idling thereof, the control of the position of each of the nozzle vanes is performed in the vicinity of a fully opened position of the variable nozzle by setting the fully opened position thereof as an initial position thereof.
Also, another example of the related art is configured in such a way as to have a duty solenoid valve, the opening of which is adjusted by adjusting an air pressure through the use of an actuator, for example, a negative pressure actuator to thereby adjust an amount of intake air of the engine. Further, the duty solenoid valve operates by receiving a control signal from an engine ECU disposed among a pressure adjusting chamber, a negative pressure chamber, and an atmospheric pressure chamber of the engine. The negative pressure chamber of the engine receives a negative pressure from a vacuum pump and adjusts the pressure and causes the negative pressure actuator to operate. The opening of the variable nozzle provided in the turbocharger and used for enabling the flow rate of the exhaust gas to vary is controlled by the operation of the negative pressure actuator.
[Patent Document 1] JP-A-2001-107738
As described above, the related art according to the JP-A-2001-107738 is configured as follows. That is, in the variable nozzle turbocharger control apparatus for an internal combustion engine, the variable nozzles, which are operated by the operation piece 4, are provided in a path of the exhaust gas blown against the turbine wheels. The flow rate of the exhaust gas is adjusted by opening and closing the variable nozzles through the use of the ring plates. Upon occurrence of abnormality in the variable nozzle turbocharger control apparatus for an internal combustion engine, upon cold start thereof, or upon idling thereof, the opening of each of the nozzle vanes is controlled by determining the initial positions of the variable nozzles. Also, drive-operations of the vanes of the variable nozzles are performed by rotation operations of the stepping motor 3.
Thus, according to this related art, the openings of the vanes of the variable nozzles are uniformly identified and determined according to the initial positions of the variable nozzles. Because of open-loop control, when deformation occurs in the operation piece and so on, the opening of each of the vanes is deviated from a target opening, so that correction control cannot be achieved. Consequently, it has been difficult to rationally control the position of each of the nozzle vanes in real time.
An object of the invention is to control an actual opening position of the vane of each of the variable nozzles by providing an electronic control actuator in a system or apparatus according to the invention, by calculating a vane opening target position of each of the variable nozzles, which is to be realized by an electronic control actuator, according to vane indication opening information supplied from an engine ECU through a control signal line to thereby control the opening of the vane of each of the variable nozzles provided in a turbocharger, and by furthermore indirectly detecting an actual opening position of each of the variable nozzles through the use of an angle sensor and rationally controlling the opening of the vane of each of the variable nozzles through the use of a feedback loop, which is a closed loop, in real time, and to surely drive the vane of each of the variable nozzles within an angle of rotation (or turn) thereof by setting an angle of rotation (or turn) of an output shaft of the electronic control actuator to be larger than the angle of rotation (or turn) of the vane of each of the variable nozzles.
Further, in addition to the aforementioned object, another object of the invention is to prevent severe collision between a lever, which is connected to the output shaft, and a stopper in a fully opened or closed position due to aged deterioration of inner mechanisms or various kinds of elements, which is resulted from long-term use thereof, and to change in ambient temperature and to variation in voltage and in external load by setting a fully opened or closed offset region that is used by a calculating device, which is provided in an electronic control circuit of the electronic control actuator, so as to preliminarily regulate and control opening/closing operations of the lever of the turbocharger within the entire mechanical operating region, and is also to prevent damage and breakage of inner constituent components of the electronic control actuator, which would be caused by such a collision.